GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 Escalade 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L80-E/4L85-E 🢒 DTC P0756

Object Number: 40795 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics

Circuit Description

The 2-3 shift solenoid (SS) valve controls fluid flow acting on the 2-3 shift valve. The 2-3 SS valve is a normally open exhaust valve used with the 1-2 SS valve in order to allow for 4 different shift combinations.

When the transmission control module (TCM) detects a 4-3-3-4 gear ratio, then DTC P0756 sets. DTC P0756 is a type A DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0756 2-3 Shift Solenoid Valve Performance - No First or Second Gear

Conditions for Running the DTC
    • No AT ISS DTCs P0716 or P0717.
    • No OSS DTCs P0722 or P0723.
    • No TCC stuck ON DTC P0742.
    • No transmission component slipping DTC P0894.
    • No shift solenoid electrical DTCs P0973, P0974, P0976 or P0977.
    • The system voltage is 8-18 volts.
    • The engine is running for more than 5 seconds.
    • The transmission OSS is 150 RPM or greater.
    • The transmission ISS is between 150 RPM and 6500 RPM.
    • The calc. throttle position is 8 percent or greater.
    • The transmission fluid temperature (TFT) is between 20°C (68°F) and 130°C (266°F).
    • The engine torque is greater than 50 N·m (37 lb ft).

Conditions for Setting the DTC

The following conditions both occur twice in one trip:

Condition 1

The TCM commands 1st gear, and the gear ratio indicates 4th gear, 0.98:1 to 1.03:1 for 2.5 seconds or greater.

Condition 2

The TCM commands 2nd gear, and the gear ratio indicates 3rd gear, 0.98:1 to 1.03:1 for 3 seconds or greater.

Action Taken When the DTC Sets
    • The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
    • The TCM commands a soft landing to 2nd gear.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores DTC P0756 in TCM history.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool can clear the DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids
    • Verify that the transmission meets the specifications in the Shift Speed table. Refer to Shift Speed .
    • Other internal transmission failures may cause more than one shift to occur.
    • The customer may have a concern with an engine over-rev condition or neutral condition in 4th gear.
    • DTC P0756 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests that the TCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.

Step

Action

Value

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: Before clearing the DTC, use the scan tool in order to record the ECM and TCM Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the ECM and TCM.

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Drive the vehicle in D4 range under the following conditions:

    6. Accelerate the vehicle, ensuring that the TCM commands 1st, 2nd, 3rd and 4th gears.

Did you detect a 4-3-3-4 shift pattern?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3
  1. Inspect the shift solenoid/hydraulic circuit for the following conditions:
    2. • 2-3 shift solenoid mechanically stuck ON
    • Refer to Shift Solenoid Leak Test .
    • 2-3 shift valve stuck in the applied position
    • A cracked 2-3 shift solenoid
    • Damaged seals on the shift solenoid valves
    • Refer to Shift Solenoid Leak Test .
  2. Clean and inspect the related valves, bores and the valve body for debris or contamination restricting oil flow. Refer to Control Valve Body Cleaning and Inspection .

Did you find and correct the condition?

--

Go to Step 4

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4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Drive the vehicle in D4.
    • Calc. throttle position is 8% or greater.
    • Ensure that the gear ratios are as specified for 1st and 2nd gear for 0.9 second or greater.
  4. Select Specific DTC.
  5. Enter DTC P0756.

Has the test run and passed?

1st: 2.42:1 to 2.52:1

2nd: 1.44:1 to 1.50:1

Go to Step 5

Go to Step 2

5

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK